Brake Light - How to Test For Power to LEDs

I understand that the brake light on the Gen 2 Prius is a set of LEDs that cannot be repaired by replacing the LED subassembly.

I also understand that if all of the segments fail at the same time the cause is may well be a circuit failure to this part of the tail-light assembly, e.g., a ground failure, a break in the circuit between the switch on the brake pedal and the assembly, etc.

Has anyone worked out a protocol for checking this out before ordering a replacement tail light (~$150 on Amazon?) Is there a simple way to 'isolate' the tail light and apply an appropriate voltage to check if the LEDs still work? Is there a link that describes the connections to the tail light assembly and designates which pin/socket connection is for the brake light? I know enough about LEDs to know that red LEDs typically require 1.8 v DC and that they are protected by a dropping resistor. In the Prius tail light is this part of the brake light sub-assembly so that the applied voltage is the expected 12V DC?

I have read that dealership service departments routinely remove/replace as the first step.

I have read at least one thread where remove/reinstall solved a brake light failure.

I would prefer testing to leaping to remove/reinstall just because it worked for someone.

I don't want to reinvent wheels that already exist. I appreciate that the approach I ask about is probably 'generation specific' and that it is not easy to search for help that is generation specific.

thanks
baumgrenze

 

I've persisted and found this reference:

Brake light wiring | PriusChat

It is a question, answer, and thanks.

I need help with the answer:

Yes, same wire. Junction J31 is the branch point, just inside of where the gas tank door is. Different ground points for the two lights. The left and right lights ground to the middle just below the hatch. The center light grounds to the hatch.​

On my '04 the left and center brake lights work, the right (passenger) does not. This suggests perhaps checking for a bad right ground before trying to replace the assembly. Does this make sense?

If so, what does nh7o mean by: "The left and right lights ground to the middle just below the hatch. The center light grounds to the hatch."

thanks
baumgrenze